Commonly-owned U.S. Pat. No. 4,642,833 to Stoltz, et al. (the “Stoltz Patent”) discloses various valve assemblies useful for automatic swimming pool cleaners. These assemblies typically include flexible diaphragms surrounded by chambers, with the diaphragms interposed in the fluid-flow paths (i.e. “in-line”) through the cleaners. In response to variation in pressure internally and externally, the diaphragms contract and expand transversely along at least part of their lengths, thereby controlling fluid flow therethrough.
Typical diaphragms of the Stoltz Patent are tubular and made of an elastic material. As noted in the Stoltz Patent:                Where the tubular member is made from elastic material it may be made to have a downstream portion less elastic than the remainder and the length of the less elastic part of the tubular member may vary circumferentially adjacent the more elastic portion and the tubular member may be reinforced with fabric or other stranded material.See Stoltz Patent, col. 1, 11. 62- 68. Also described in the Stoltz Patent are inner circumferential ribs “extending along substantially 180° of the surface of the diaphragm and on opposite sides thereof.” Id., col. 2, 11. 38-40 (numeral omitted). These circumferential ribs facilitate closing the diaphragms so as to prevent fluid from flowing therethrough. See id., col. 3, 11. 20-22.        
Commonly-owned U.S. Pat. No. 4,742,593 to Kallenbach (the “Kallenbach Patent”) discloses additional valve assemblies for use with automatic swimming pool cleaners. These assemblies, also typically tubular and of flexible material, too may be interposed in-line, within the fluid-flow paths of such cleaners. According to the Kallenbach Patent:                The body [of the tubular valve] has an intermediate section between the ends that assumes a substantially collapsed condition over a segment thereof in absence of a pressure differential between the interior and exterior. The section preferably is collapsed transversely over a segment.        Along the collapsed segment, the body has diverging interior walls in the direction of water flow therethrough. The walls diverge from a substantially constant diameter that extends for a portion of the section adjacent the first end to a substantially constant, but larger, diameter that extends for a portion of the section adjacent the second end. Further, the divergence is a substantially linear function of the distance along the segment.See Kallenbach Patent, col. 1, 11. 28-42. Also noted in the Kallenbach Patent is that        The section may be provided with longitudinal reinforcing ribs on each side extending from near the second end to the collapsed segment.        Further, vertical ribbing may be provided on the interior of the section on opposing surfaces proximate the collapsed segment.Id. at 11. 43-47. At least some of the longitudinal ribs are designed to “serve as a means for stiffening the valve member in the axial or longitudinal direction.” Id, col. 3, 11. 53-55.        
International Publication No. WO 02/01022 of Kallenbach, et al. (the “Kallenbach Publication”), entitled “Swimming Pool Cleaner,” details another cleaner in which a valve periodically interrupts a flow of water through the body of the cleaner. Included in the cleaner are a main flow path and a by-pass passage built into the body. See Kallenbach Publication, p. 5, 11. 8-11. Also included in one version is an “annular resilient rolling diaphragm” with an edge “located in sealing engagement with the inner wall of the body.” Id., p. 6, 11. 24-26. However, a dome-shaped valve closure member, rather than the rolling diaphragm, operates to interrupt fluid flow through the main path. Additionally, neither the rolling diaphragm nor the dome-shaped member is interposed in-line in the main water path from the inlet passage of the cleaner to the outlet of the body.
Each of the Stoltz and Kallenbach Patents and the Kallenbach Publication discusses “suction-side” cleaners in which a pair of concentric pipes exist, the outer of the pipes being adapted for connection to a flexible hose leading (directly or indirectly) to the inlet, or “suction side,” of a pump. An annular gap between the pipes permits water to flow through the by-pass passage of the cleaner of the Kallenbach Publication toward the flexible hose. A similar gap in versions of cleaners discussed in the Stoltz and Kallenbach Patents offers “suction communication . . . through slots [in a plate] to [a] chamber” defined at least in part by the tubular members of these patents. The contents of the Kallenbach Publication, together with those of the Stoltz and Kallenbach Patents, are incorporated herein in their entireties by this reference.